Why does a zener diode work in reverse bias?
A zener diode is designed to allow a current to flow through it in a direction that is reverse to the normal flow of current that would occur if it were used as a rectifier. Current can flow through a zener diode in both directions. In the forward direction, current will flow at a low voltage, usually about 1 volt. In the reverse direction, no current will flow until the voltage impressed across it is equal to the zener voltage. At this point, a current will flow and an extremely small increase in voltage will cause a large increase in current. Most importantly, it should be noted that the current flow through the zener diode is in the reverse direction to that of a normal rectifier.
With the application of sufficient reverse voltage, a p-n junction will experience a rapid avalanche breakdown and conduct current in the reverse direction. Valence electrons which break free under the influence of the applied electric field can be accelerated enough that they can knock loose other electrons and the subsequent collisions quickly become an avalanche. When this process is taking place, very small changes in voltage can cause very large changes in current. The breakdown process depends upon the applied electric field, so by changing the thickness of the layer to which the voltage is applied, zener diodes can be formed which break down at voltages from about 4 volts to several hundred volts.
Difference between FM and AM, which is preferred & its advantages.
AM and FM are methods of delivering signals embedded in a carrier frequency. There are many applications for them but they are best known for radio applications
AM means amplitude modulation. In this technique, the amplitude or height of the carrier signal increases and decreases as the base signal changes. AM radio signals will travel great distances so a single transmitter can cover large areas.
FM means Frequency Modulation where the frequency of the carrier signal increases and decreases to represent the change in voltage of the base signal. FM signals tend to offer better signal quality than AM but the range is far less, demanding multiple transmitters to cover the same area as one AM transmitter.
AM means amplitude modulation. In this technique, the amplitude or height of the carrier signal increases and decreases as the base signal changes. AM radio signals will travel great distances so a single transmitter can cover large areas.
FM means Frequency Modulation where the frequency of the carrier signal increases and decreases to represent the change in voltage of the base signal. FM signals tend to offer better signal quality than AM but the range is far less, demanding multiple transmitters to cover the same area as one AM transmitter.
To what does RS-232 refer?
It refers to the 25-pin or 9-pin male serial port on the back of a PC.
"A serial port conforms to the interface standard called RS-232c (Reference Standard 232 revision c), which is why a serial port is sometimes called the RS-232 port. The maximum cable length for a serial cable according to RS-232 standards is 50 feet. This interface standard originally called for 25 pins, but because microcomputers use only nine of those pins, manufacturers often installed a modified 9-pin port."
"A serial port conforms to the interface standard called RS-232c (Reference Standard 232 revision c), which is why a serial port is sometimes called the RS-232 port. The maximum cable length for a serial cable according to RS-232 standards is 50 feet. This interface standard originally called for 25 pins, but because microcomputers use only nine of those pins, manufacturers often installed a modified 9-pin port."
What is Lenz law ?
A law of electromagnetism which states that, whenever there is an induced electromotive force (emf) in a conductor, it is always in such a direction that the current it would produce would oppose the change which causes the induced emf. If the change is the motion of a conductor through a magnetic field, the induced current must be in such a direction as to produce a force opposing the motion. If the change causing the emf is a change of flux threading a coil, the induced current must produce a flux in such a direction as to oppose the change.
Lenz's law is a form of the law of conservation of energy, since it states that a change cannot propagate itself.
What is Transmission Frequency of Bluetooth, Wi-Fi and Wi-MAX ?
Wi-Fi is transmitted at different rates according to IEEE 802.11
There are also different letters that specify speed (example: 802.11n)
There are also different letters that specify speed (example: 802.11n)
This varies on what wireless device you use.
A typical wi-fi home router using 802.11b or 802.11g with a stock antenna might have a range of 32 m (120 ft) indoors and 95 m (300 ft) outdoors. The new IEEE 802.11n however, can apperently exceed that range by more than double (nearly 200m)
A typical wi-fi home router using 802.11b or 802.11g with a stock antenna might have a range of 32 m (120 ft) indoors and 95 m (300 ft) outdoors. The new IEEE 802.11n however, can apperently exceed that range by more than double (nearly 200m)
What is difference between Piconet and Scatternet ?
Meaning "tiny" network, a piconet is a Bluetooth network composed of two or more Bluetooth devices that operate in close proximity on the same channel and frequency hopping sequence. Piconets operate in both ad hoc (peer-to-peer) and infrastructure (central base station) modes of operation.
Masters, Slaves and Scatternets
In a piconet, one device is the master, which establishes the frequency hopping scheme, and there can be up to seven active and 255 inactive slave devices. However, a slave in one piconet can be a master in another, creating a chain of piconets called a "scatternet" that extends the distance between all devices. See Bluetooth.
What is Moore's Law ?
(computer science) The prediction by Gordon Moore (cofounder of the Intel Corporation) that the number of transistors on a microprocessor would double periodically (approximately every 18 months).
"The number of transistors and resistors on a chip doubles every 18 months." By Intel co-founder Gordon Moore regarding the pace of semiconductor technology. He made this famous comment in 1965 when there were approximately 60 devices on a chip. Proving Moore's law to be rather accurate, four decades later, Intel placed 1.7 billion transistors on its Itanium chip.
"The number of transistors and resistors on a chip doubles every 18 months." By Intel co-founder Gordon Moore regarding the pace of semiconductor technology. He made this famous comment in 1965 when there were approximately 60 devices on a chip. Proving Moore's law to be rather accurate, four decades later, Intel placed 1.7 billion transistors on its Itanium chip.
In 1975, Moore extended the 18 months to 24 months. More recently, he said that the cost of a semiconductor manufacturing plant doubles with each generation of microprocessor.
How many satellites comprise the GPS and expand it ?
There are at least 24 GPS satellites in operation at any given time with a number of on-orbit spares in case one fails. Each one is in a 12 hour orbit (meaning it takes 12 hours to orbit the earth). They are in a variety of six different orbits and are not just locked into a geosynchronous orbit (meaning they stay over roughly the same place on earth at all times, like your satellite TV and communications satellites) like some satellites.
All GPS satellites are owned and operated by the US Air Force and are controlled specifically by the 2d Space Operations Squadron at Schriever AFB in Colorado Springs, CO. There is not an easy way to deny the GPS capability to our enemies without also denying our own capability, so it is a free system open to anyone that has the technology to utilize it.
GPS satellites carry not only positional data but also extremely precise timing signals, which help the GPS receivers on the ground to triangulate their position and are even used to validate and secure financial transactions, etc. When the system was first created, artificial timing errors were put into the signal to try to reduce the effectiveness of the system for non-military users, but it was removed in 2000.
The GPS satellites also have NUDET (Nuclear Detonation) sensors on them to detect nuclear detonations almost anywhere on earth.
To use GPS you need to be in clear view of at the very least 3 satellites but you should be in view of 6 satellites at any given time unless some are blocked by objects, mountains, etc. So, GPS usually doesn't work well in-doors or even in a forrest or valley at times.
What is ZigBee and its specifications ?
ZigBee is a standard (rules, specifications, etc.) of a wireless network. This network aims specifically for home devices and appliances by making each 'node' 'speaks' with another, and benefit from each other.
What is FPGA ?
(Field Programmable Gate Array) A type of gate array that is programmed in the field rather than in a semiconductor fab. Containing up to hundreds of thousands of gates, there are a variety of FPGA architectures on the market. Some are very sophisticated, including not only programmable logic elements, but programmable interconnects and switches between the elements. The interconnects take up a lot of FPGA real estate, resulting in a chip with very low gate density compared to ASICs. In 2008, Altera introduced its Stratix IV FPGA with 2.5 billion transistors and 680K logic elements.
The vast majority of FPGAs are SRAM-based, although there are some flash and antifuse versions. The antifuse varieties are of interest to aerospace designers because they are more radiation hardened (rad hard). See PLD and adaptive computing.
What is MIMO ?
(Multiple Input/Multiple Output) Pronounced "my-mo," it is the use of multiple transmitters and receivers (multiple antennas) on wireless devices for improved performance. When two transmitters and two or more receivers are used, two simultaneous data streams can be sent, which double the data rate. Multiple receivers alone allow greater distances between devices. For example, the IEEE 802.11n (Wi-Fi) wireless standard uses MIMO to increase speed to 100 Mbps and beyond, doubling at minimum the 802.11a and 11g rates. MIMO antennas are also used in WiMAX and LTE.
MIMO, MISO and SIMO
The M, S, I and O relate to the air, not the device. For example, multiple inputs (MI) means multiple transmitters send multiple data streams "into" the air. Multiple outputs (MO) means multiple receivers acquire multiple data streams "out of" the air (see illustration below). See 802.11n, antenna diversity, beamforming and HSPA.
ARCHITECTURE AND ADVANTAGES OF
MULTIPLE ANTENNA TECHNOLOGIES
Compared to
Single Antenna (SISO)
Technologies
Transmit Receive Data
Type Antennas Antennas Rate Distance
MIMO Multiple Multiple Greater Greater range
MISO Multiple Single Same Same range but
More Reliable
SIMO Single Multiple Same Greater range
M = Multiple S = Single
I = Input O = Output
MIMO Wireless Router |
This "Pre-N" wireless router from Belkin uses two transmitters and three receivers to provide 108 Mbps between its access point and Belkin Pre-N cards in laptops. Introduced in 2004, this was the first "Preliminary-802.11n" system on the market (see 802.11n). (Image courtesy of Belkin Corporation, www.belkin.com)
What is VOIP ?
(Voice Over IP) A digital telephone service that uses the public Internet and private backbones for call transport. Support for the public switched telephone network (PSTN) is also provided so that VoIP calls can originate and terminate from regular telephones. Many companies, including Vonage, 8x8 and AT&T (CallVantage), typically offer calling within the country for a fixed fee and a low per-minute charge for international. Customers are required to have broadband Internet access (cable or DSL).
Handset Based
Regular phones can be used with many VoIP services by plugging them into an analog telephone adapter (ATA) provided by the VoIP provider or purchased from a third party. The ATA converts the phone to IP packets. IP phones can also be used that have built-in IP packet support.
Softphone Based
VoIP providers may be entirely softphone based, which requires a computer, phone software and microphone and speakers (or headset) to make and receive calls. Usually free of cost if both sides are on the same service, softphones let users call any phone in the world from their laptops and an Internet connection. Per-minute charges apply to call a regular phone number, but calls from a regular phone may not be possible. In 1995, VocalTec Communications introduced the first VoIP service in the U.S., and it was softphone based (see Internet Phone).
VoIP Features
Voicemail, caller ID, call forwarding and a softphone option (if not a softphone-only service) are typically part of a VoIP package. Phone numbers with area codes outside of one's own home area may also be an option (see virtual phone number). See IP telephony for more details and history of
On what principle do Transformers work ?
The transformer is based on two principles: firstly, that an electric current can produce a magnetic field (electromagnetism) and secondly that a changing magnetic field within a coil of wire induces a voltage across the ends of the coil (electromagnetic induction). Changing the current in the primary coil changes the magnitude of the applied magnetic field. The changing magnetic flux extends to the secondary coil where a voltage is induced across its ends.
A transformer is a device which is use to convert high alternatic voltage to a low alternatic voltage and vice versa.
A transformer is a device which is use to convert high alternatic voltage to a low alternatic voltage and vice versa.
WORKING PRINCIPLE
Transformer works on the principle of mutual induction of two coils. When current in the primary coil is changed the flux linked to the secondary coil also changes. Consequently an EMF is induced in the secondary coil.
CONSTRUCTION
A transformer consists of a rectangular core of soft iron in the form of sheets insulated from one another. Two separate coils of insulated wires, a primary coil and a secondary coil are wound on the core. These coils are well insulated from one another and from the core. The coil on the input side is called Primary coil and the coil on the output side is called Secondary coil
What is EDFA ?
(Erbium-Doped Fiber Amplifier) A device that boosts the signal in an optical fiber. Introduced in the late 1980s, the EDFA was the first successful optical amplifier. It was a major factor in the rapid development of fiber-optic networks in the 1990s, because it extended the distance between costly regenerators. In addition, an EDFA amplifies all the channels in a WDM signal simultaneously, whereas regenerators require optical to electrical conversion for each channel.
A Laser Without Mirrors
Functioning like a laser without mirrors, the EDFA uses a semiconductor pump laser to introduce a powerful beam at a shorter wavelength into a section of erbium-doped fiber several meters long. The pump light excites the erbium atoms to higher orbits, and the input signal stimulates them to release excess energy as photons in phase and at the same wavelength. EDFAs boost wavelengths in the 1550 nm range, and the pump light is typically 1480 nm or 980 nm. See EDWA, WDM, Raman amplifier and optical amplifier.
EDFAs boost the input regardless of the number of wavelengths. In several meters of doped fiber, the pump laser excites the doped atoms to higher orbits, and the input signal stimulates them to release excess energy as photons in phase and at the same wavelength. (Illustration courtesy of Jeff Hecht.)What are different types of antennas ?
There are different types of antennas,they can mainly devided into directional & undirectional
a simply type of directional antennas: helical antenna
a simple type of undirectional antennas:yagi & loop antennas
What is Yagi-Uda antenna ?
(electromagnetism) An end-fire antenna array having maximum radiation in the direction of the array line; it has one dipole connected to the transmission line and a number of equally spaced unconnected dipoles mounted parallel to the first in the same horizontal plane to serve as directors and reflectors. Also known as Uda antenna; Yagi antenna.
What is latest satellite from ISRO?
PSLV-C15
What is meant by D-FF?
(D-flip flop stands for Delay flip-flop, it delays input by one clock pulse)
What is the basic difference between Latches and Flip flops?
(Latches are monostable and flip-flops are bistable)
What is a multiplexer?
(It is used to multiplex data from different sources normally used in TDM)
How can you convert an SR Flip-flop to a JK Flip-flop?
How can you convert an JK Flip-flop to a D Flip-flop?
( Connect J to D and K to not(D))
What is Race-around problem? How can you rectify it?
( Race around condition occurs in a JK flip-flop when both the inputs are set to '1', it can be rectified using edge-triggered flip-flop or using master-slave flip-flops)
Which semiconductor device is used as a voltage regulator and why?
What do you mean by an ideal voltage source?
What do you mean by zener breakdown and avalanche breakdown?
( zener breakdown takes place when very high voltage is applied to the diode this results in very high reverse current, as voltage is further increased minority carriers gain further momentum and strike atoms releases more carriers, which results in further increase in temp. It becomes vicious cycle and leads to avalanche breakdown or on other words "thermal runaway".
What are the different types of filters?
( analog filters n digital filters not sure wht u meant)
What is the need of filtering ideal response of filters and actual response of filters?
What is sampling theorem?
( sampling frequency should be atleast twice the maximum freq present in the signal)
What is impulse response?
( response given by a digital system when impulse signal is applied to it. Used to find out stability of system)
Explain the advantages and disadvantages of FIR filters compared to IIR counterparts.
What is CMRR? Explain briefly.
( Common mode rejection ratio)
What do you mean by half-duplex and full-duplex communication? Explain briefly.
( half-duplex: either sender or receiver can use the channel at one time eg walky-talky and full-duplex: sender or receiver or both can use the channel at one time eg telephone)
Which range of signals are used for terrestrial transmission?
What is the need for modulation?
Which type of modulation is used in TV transmission?
( video signal: vestigial side band modulation and audio signal: FM)
Why we use vestigial side band (VSB-C3F) transmission for picture?
( why not DSBSC: large bandwidth req.why not SSBSC: To over come distortion by filters used at receivers thus demodulation becomes complex hence costly)
When transmitting digital signals is it necessary to transmit some harmonics in addition to fundamental frequency?
( yup but not sure why)
For asynchronous transmission, is it necessary to supply some synchronizing pulses additionally or to supply or to supply start and stop bit?
( for asyn tx it is necessary to use start and stop bits as no common clock is there)
BPFSK is more efficient than BFSK in presence of noise. Why?
What is meant by pre-emphasis and de-emphasis?
( used in TV Tx for voice signal not sure why)
What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB? What do you mean by ASCII, EBCDIC?
1.What are the flags in 8086?
Carry flag, Parity flag, Auxiliary carry flag, Zero flag, Overflow flag, Trace flag, Interrupt flag, Direction flag, and Sign flag.
2.What are the various interrupts in 8086??
Maskable interrupts, Non-Maskable interrupts
3.What is meant by Maskable interrupts?
An interrupt that can be turned off by the programmer is known as Maskable interrupt.
4.Which interrupts are generally used for critical events??
Non-Maskable interrupts are used in critical events Such as Power failure, Emergency, Shut off etc.
5.What is the Maximum clock frequency in 8086?
5 Mhz is the Maximum clock frequency in 8086.
6.What are the various segment registers in 8086?
Code, Data, Stack, Extra
7.Which Stack is used in 8086?
FIFO (First In First Out) stack is used in 8086.In this type of Stack the first stored information is retrieved first.
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1.What are the various registers in 8085?
Accumulator register, Temporary register, Instruction register, Stack Pointer, Program Counter are the various registers in 8085 .
2.What is Stack Pointer
Stack pointer is a special purpose 16-bit register in the Microprocessor, which holds the address of the top of the stack
3.What is Program counter?
Program counter holds the address of either the first byte of the next instruction to be fetched for execution or the address of the next byte of a multi byte instruction, which has not been completely fetched. In both the cases it gets incremented automatically one by one as the instruction bytes get fetched. Also Program register keeps the address of the next instruction.
4.Which Stack is used in 8085?
LIFO (Last In First Out) stack is used in 8085.In this type of Stack the last stored information can be retrieved first.
5.What is meant by a bus?
A bus is a group of conducting lines that carriers data, address, & control signals.
6.What is Tri-state logic?
Three Logic Levels are used and they are High, Low, High impedance state. The high and low are normal logic levels & high impedance state is electrical open circuit conditions. Tri-state logic has a third line called enable line.
7.Give an example of one address microprocessor?
8085 is a one address microprocessor.
8.In what way interrupts are classified in 8085?
In 8085 the interrupts are classified as Hardware and Software interrupts.
9.examples of Software interrupts?
RST0, RST1, RST2, RST3, RST4, RST5, RST6, RST7.
10.EXAMPLES of Hardware interrupts?
TRAP, RST7.5, RST6.5, RST5.5, INTR.
11.Which interrupt has the highest priority?
TRAP has the highest priority.
12.Name 5 different addressing modes?
Immediate, Direct, Register, Register indirect, Implied addressing modes.
13.How many interrupts are there in 8085?
There are 12 interrupts in 8085.
14.What is clock frequency for 8085?
3 MHz is the maximum clock frequency for 8085.
15.In 8085 which is called as High order / Low order Register?
Flag is called as Low order register & Accumulator is called as High order Register.
16.Why crystal is a preferred clock source?
Because of high stability, large Q (Quality Factor) & the frequency that doesn't drift with aging. Crystal is used as a clock source most of the times.
17.What does Quality factor mean?
The Quality factor is also defined, as Q. So it is a number, which reflects the lossness of a circuit. Higher the Q, the lower are the losses.
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1.what is the differnce between SCR and diode rectifier?
ans: diode is a 2 terminal device, in scr gate controls the rectifing.SCR is used in High frequency applications but diode is low freuency devices, SCR can be in high temparatures but not diode.
2.whatis intersymbol interference
ans:In telecommunication, intersymbol interference (ISI) means a form of distortion of a signal that causes the previously transmitted symbols to have an effect on the currently received symbol. This is usually an unwanted phenomenon as the previous symbols have similar effect as noise, thus making the communication less reliable. ISI is usually caused by echoes or non-linear frequency response of the channel. Ways to fight against intersymbol interference include adaptive equalization or error correcting codes (especially soft-decoding with Viterbi algorithm).
3.Distinguish between Angle modulation and Amplitude modulation.
ans: In amplitude Modulation as the amplitude of given signal varies, the amplitude of carrier signal also varies in the same way.
In angle modulation, the frequency or phase may vary according to the amplitude of given signal
4.What is Biasing?
ans: biasing is a process of connecting dc voltage to a device by which we can select the operating point of the device. by biasing actually we select the operating point of the device.
5.What do you mean by ASCII, EBCDIC?
ans:ASCII (American Standard Code for Information Interchange), is a character encoding based on the English alphabet.
EBCDIC (Extended Binary Coded Decimal Interchange Code) is an 8-bit character encoding used on IBM mainframe operating systems
6.What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB?
ans:3db implies 70%(o.7o7) of the power,i'e we r interested to consider the bandwidth range from peak to 70% b'coz uptp 70% its reliable.hence 3db is called as half power freq. 3db value is the mean square value which is 70% of the maximum value.
7.What is meant by pre-emphasis and de-emphasis?
ans:Pre-emphasis
" Improving the signal to noise ratio by increasing the magnitude of higher frequency signals with respect to lower frequency signals"
De-emphasis
" Improving the signal to noise ratio by decreasing the magnitude of higher frequency signals with respect to lower frequency signals"
8.What is sampling theorem?
ans:It is defined as the sampling frequency should be greater than or equal to twice the sampling frequency then we can generate the original signal if the condition does not satisfy we get the signal in the distorted mannerit is given as ( fs >/ 2 fs)
9.What is Race-around problem? How can you rectify it?
ans: A condition in logic network in which the difference in propagation times through two or more signal paths in the network can produce an erroneous output.in jk flip flop race around problem will occur when both the inputs are high. it can be prevented by using master slave jk flip flop
10.What is the basic difference between Latches and Flip flops?
ans:latch works without clock signal,but works with a control signal and it is level triggered device.whereas flip flop is a 1 bit storage element and works with a clock signal.its a edge triggered device. normally latches are avoided and flip flops are preferred.
11. what is Barkhausen Criterion?
ans:
1./AB/=1,i.e. the magnitude of loop gain must be unity
2.the total prase shift around the closed loop is zero or 360 degrees.
12.what are active and Passive Components?
ans:ACTIVE COMPONENTS The components which produce the energy in the form of current or voltage are called as active components.Example:transistors etc,.
PASSIVE COMPONENTS
The components which stores the energy in the form of current or voltage are called as passive components.example:inductors,resistors,capacitors etc
Carry flag, Parity flag, Auxiliary carry flag, Zero flag, Overflow flag, Trace flag, Interrupt flag, Direction flag, and Sign flag.
2.What are the various interrupts in 8086??
Maskable interrupts, Non-Maskable interrupts
3.What is meant by Maskable interrupts?
An interrupt that can be turned off by the programmer is known as Maskable interrupt.
4.Which interrupts are generally used for critical events??
Non-Maskable interrupts are used in critical events Such as Power failure, Emergency, Shut off etc.
5.What is the Maximum clock frequency in 8086?
5 Mhz is the Maximum clock frequency in 8086.
6.What are the various segment registers in 8086?
Code, Data, Stack, Extra
7.Which Stack is used in 8086?
FIFO (First In First Out) stack is used in 8086.In this type of Stack the first stored information is retrieved first.
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1.What are the various registers in 8085?
Accumulator register, Temporary register, Instruction register, Stack Pointer, Program Counter are the various registers in 8085 .
2.What is Stack Pointer
Stack pointer is a special purpose 16-bit register in the Microprocessor, which holds the address of the top of the stack
3.What is Program counter?
Program counter holds the address of either the first byte of the next instruction to be fetched for execution or the address of the next byte of a multi byte instruction, which has not been completely fetched. In both the cases it gets incremented automatically one by one as the instruction bytes get fetched. Also Program register keeps the address of the next instruction.
4.Which Stack is used in 8085?
LIFO (Last In First Out) stack is used in 8085.In this type of Stack the last stored information can be retrieved first.
5.What is meant by a bus?
A bus is a group of conducting lines that carriers data, address, & control signals.
6.What is Tri-state logic?
Three Logic Levels are used and they are High, Low, High impedance state. The high and low are normal logic levels & high impedance state is electrical open circuit conditions. Tri-state logic has a third line called enable line.
7.Give an example of one address microprocessor?
8085 is a one address microprocessor.
8.In what way interrupts are classified in 8085?
In 8085 the interrupts are classified as Hardware and Software interrupts.
9.examples of Software interrupts?
RST0, RST1, RST2, RST3, RST4, RST5, RST6, RST7.
10.EXAMPLES of Hardware interrupts?
TRAP, RST7.5, RST6.5, RST5.5, INTR.
11.Which interrupt has the highest priority?
TRAP has the highest priority.
12.Name 5 different addressing modes?
Immediate, Direct, Register, Register indirect, Implied addressing modes.
13.How many interrupts are there in 8085?
There are 12 interrupts in 8085.
14.What is clock frequency for 8085?
3 MHz is the maximum clock frequency for 8085.
15.In 8085 which is called as High order / Low order Register?
Flag is called as Low order register & Accumulator is called as High order Register.
16.Why crystal is a preferred clock source?
Because of high stability, large Q (Quality Factor) & the frequency that doesn't drift with aging. Crystal is used as a clock source most of the times.
17.What does Quality factor mean?
The Quality factor is also defined, as Q. So it is a number, which reflects the lossness of a circuit. Higher the Q, the lower are the losses.
------------------------------------------------------------------------------------------------------------------------------------------------------------------
1.what is the differnce between SCR and diode rectifier?
ans: diode is a 2 terminal device, in scr gate controls the rectifing.SCR is used in High frequency applications but diode is low freuency devices, SCR can be in high temparatures but not diode.
2.whatis intersymbol interference
ans:In telecommunication, intersymbol interference (ISI) means a form of distortion of a signal that causes the previously transmitted symbols to have an effect on the currently received symbol. This is usually an unwanted phenomenon as the previous symbols have similar effect as noise, thus making the communication less reliable. ISI is usually caused by echoes or non-linear frequency response of the channel. Ways to fight against intersymbol interference include adaptive equalization or error correcting codes (especially soft-decoding with Viterbi algorithm).
3.Distinguish between Angle modulation and Amplitude modulation.
ans: In amplitude Modulation as the amplitude of given signal varies, the amplitude of carrier signal also varies in the same way.
In angle modulation, the frequency or phase may vary according to the amplitude of given signal
4.What is Biasing?
ans: biasing is a process of connecting dc voltage to a device by which we can select the operating point of the device. by biasing actually we select the operating point of the device.
5.What do you mean by ASCII, EBCDIC?
ans:ASCII (American Standard Code for Information Interchange), is a character encoding based on the English alphabet.
EBCDIC (Extended Binary Coded Decimal Interchange Code) is an 8-bit character encoding used on IBM mainframe operating systems
6.What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB?
ans:3db implies 70%(o.7o7) of the power,i'e we r interested to consider the bandwidth range from peak to 70% b'coz uptp 70% its reliable.hence 3db is called as half power freq. 3db value is the mean square value which is 70% of the maximum value.
7.What is meant by pre-emphasis and de-emphasis?
ans:Pre-emphasis
" Improving the signal to noise ratio by increasing the magnitude of higher frequency signals with respect to lower frequency signals"
De-emphasis
" Improving the signal to noise ratio by decreasing the magnitude of higher frequency signals with respect to lower frequency signals"
8.What is sampling theorem?
ans:It is defined as the sampling frequency should be greater than or equal to twice the sampling frequency then we can generate the original signal if the condition does not satisfy we get the signal in the distorted mannerit is given as ( fs >/ 2 fs)
9.What is Race-around problem? How can you rectify it?
ans: A condition in logic network in which the difference in propagation times through two or more signal paths in the network can produce an erroneous output.in jk flip flop race around problem will occur when both the inputs are high. it can be prevented by using master slave jk flip flop
10.What is the basic difference between Latches and Flip flops?
ans:latch works without clock signal,but works with a control signal and it is level triggered device.whereas flip flop is a 1 bit storage element and works with a clock signal.its a edge triggered device. normally latches are avoided and flip flops are preferred.
11. what is Barkhausen Criterion?
ans:
1./AB/=1,i.e. the magnitude of loop gain must be unity
2.the total prase shift around the closed loop is zero or 360 degrees.
12.what are active and Passive Components?
ans:ACTIVE COMPONENTS The components which produce the energy in the form of current or voltage are called as active components.Example:transistors etc,.
PASSIVE COMPONENTS
The components which stores the energy in the form of current or voltage are called as passive components.example:inductors,resistors,capacitors etc
